SCHOENFUSS, H.L.*; BLOB, R.W.: Kinematics of vertical climbing in Hawaiian freshwater gobies

The Hawaiian freshwater ecosystem includes three species of waterfall climbing gobies. Larvae of these species are washed into the ocean by currents upon hatching, return to freshwater 3 to 6 months posthatching, and then climb waterfalls (up to 350 m vertically for Lentipes concolor) to reach adult habitats. We used high-speed video to contrast climbing kinematics of Sicyopterus stimpsoni (20-24 mm total length) with that of Awaous guamensis and L. concolor (both 12-16 mm TL) on a clear plexiglas waterfall. L. concolor and A. guamensis climb vertically using bursts of axial-based swimming. Bursts typically last 0.07 � 0.02 sec at velocities of 10.3 � 4.2 TL/sec (190 � 80 mm/sec). The pectoral fins extend perpendicular to the body during pauses between bursts, but adduct quickly as climbing resumes (possibly contributing to thrust initiation). In contrast, S. stimpsoni usually climb by alternately attaching oral or pelvic sucking discs to surfaces and ‘inching’ upwards with little axial undulation or fin movement. As the oral disc attaches it expands to twice its resting area, after which the posterior body is pulled upwards; once the pelvic disc attaches, the oral disc releases and the anterior body advances. Climbing bouts can include multiple cycles of disc attachment and last several seconds at velocities of 0.25 � 0.04 TL/sec (6 � 1 mm/sec). The use of power-bursts to climb may be impeded in S. stimpsoni as this species typically loses 15% of its weight during metamorphosis preceding their migration up waterfalls. By ‘inching’ up waterfalls, S. stimpsoni always remain attached to the substrate by suction at least at one point along the body. ONR N000149910184 (M. Westneat); Hawaii Fish Restoration Project F-14-R-18 (M. Fitzsimons).